1. Field of the Invention
This invention relates to magnetic domain memory circuits and particularly to interrogating and writing into such memory circuits using magnetic domain logic elements.
2. Description of the Prior Art
Recently significant interests have developed in a class of magnetic devices known generically as magnetic or "bubble" domain devices. Such devices described, for example, in IEEE Transactions on Magnetics, Vol. MAG.-5, No. 3 (1969) pp. 544-553, "Application of Orthoferrites to Domain-Wall Devices", are generally planar in configuration and are constructed of materials which have magnetically easy directions essentially perpendicular to the plane of the structure. Magnetic properties, e.g., magnetization anisotropy, coercivity, mobility, are such that the device may be maintained magnetically saturated with magnitization in a direction out of the plane and that single domain small localized regions of polarization aligned opposite to the general polarization direction may be supported. Such localized regions, which are generally cylindrical in configuration, represent memory bits. Interest in devices of this nature is, in large part, based on high density and the ability of the cylindrical magnetic domain to be independent of the boundary of the magnetic material in the plane in which it is formed and hence capable of moving anywhere in the plane of the magnetic material to effect various logic operations.
The bubbles can be manipulated by programming currents through a pattern of conductors positioned adjacent the magnetic material or by varying the surrounding magnetic field. As an example, the magnetic domains or bubbles may be formed in thin platelets having uniaxial anisotropy with the easy magnetic axis perpendicular to the plate comprising such material as rare earth orthoferrite and rare earth aluminum and gallium substituted iron garnets. Since the magnetic bubbles can be propagated, erased, replicated, and manipulated to form logic operations and their presence and absence detected, these bubbles may be utilized to perform many of the on-off or primary functions vital to computer operation.
Magnetic bubble memory systems offer significant advantages since logic, memory, counting and switching may all be performed within a single layer of solid magnetic material. This is in contrast to conventional memory systems in which information must move from one device to another through interconnecting conductors and high gain amplifiers. The magnetic bubbles representing the data move in a plane of thin sheets of magnetic material such as orthoferrite crystals, for example, and they can be shifted into precisely defined positions at high speed with little energy. The magnetic material itself remains stationary. With the advent of mixed rare earth aluminum or gallium substituted iron garnets which are capable of providing bit density in the order of 10.sup.6 per square inch, the development of a reliable solid state material memory equivalent of magnetic disc file or drums has become a particularly attractive and realistic concept.
Many organizations of operatable domains have been disclosed. One of the most popular is the major-minor memory organization disclosed in U.S. Pat. No. 3,618,054 of P. I. Bonyhard, U. F. Gianola, and A. J. Perneski. The major-minor memory organization as well as its implementation and operation is now well known in the art. Other memory organizations, including non-closed loop organizations, are also well known.
Typically, a memory organization is established by an arrangement of T and bar permalloy circuits on an orthoferrite platelet. The bubbles circularly propagate around the loop by inplane rotating magnetic field action. Access to an organization is normally performed through detect and read connections thereto and by write connections. The connections include a transfer conducting line for application of an external electrical pulse to cause a transfer of bubble data to and from the loop, as desired.
Therefore, even though the memory unit includes a plurality of individual logic storage registers, the manipulative operations are electronic. Hence, heretofore there has not been an all-bubble memory system wherein the manipulative as well as the storage operations are performed using magnetic domain operative elements.
Accordingly, it is a feature of the present invention to provide an improved accessing of a bubble logic storage register for reading the bubble logic therefrom using all-bubble read-out elements.
Another feature of the present invention is to provide an improved accessing of a bubble logic storage register for writing new bubble logic therein using all-bubble write elements.
Yet another feature of the present invention is to provide an improved accessing of a bubble logic storage register for erasing bubbles therefrom using all-bubble erase elements.
Still another feature of the present invention is to provide an improved accessing of a plurality of bubble logic storage register for reading out bubbles therefrom to a common output data stream and for erasing and writing bubbles therein from a common input data stream.